Services "start date and hour and end date and hour end" - main_use_hourmin_in_date_range

Hi all.

Need to print in pdf invoices, start date and time, and finish date and time of services.

Theres a variable: MAIN_USE_HOURMIN_IN_DATE_RANGE, but nothing chages in native PDF invoice models CRABE o SPONGE, when variable is set to 1.

¿Any help with that?, dont really know where more I could try to change something, but dont what to develop for this, since Im sure that is a native opction in PDF documents.

Regards